The answer to your question depends somewhat on the contents of the nutritional shakes you would be consuming prior to your surgery
. As long as you are getting adequate amounts of protein, the likelihood of a short time on an all liquid diet causing major health problem is quite slim. Your weight won't drop that much in 5 days, you won't become dehydrated because you would be drinking fluids, and as long as your shakes contained a balanced amount of protein, you won't become deficient.
With that said, I don't think it is necessary for you to do this. If you want to lose weight over the long run, it is better for you to develop a long term weight loss
plan that includes permanent changes to your diet and the institution of regular exercise. There is no benefit you will receive by going onto an all liquid diet 5 days prior to surgery. The only requirement is that you don't eat any food the night before your surgery.
The best physician for you to speak to about this is the surgeon
who will be performing your operation. Your surgeon will have specific recommendations that you should do prior to your surgery.